Table 2.

Substrate profiles of SHV-2, SHV-2a, and SHV-12 enzymes

β-Lactamase (pI)RelativeVmaxaSource or reference
PCNCERCTXCAZAZT
SHV-2 (7.6)10012327<111 10
SHV-2a (7.6)10021535<111This study
SHV-12 (8.2)1002144216110This study
  • a Hydrolytic activity against β-lactams was evaluated by spectrophotometry (model UVIKON 860; Kontron) at 37°C in 0.1 M phosphate buffer (pH 7.0). V maxwas calculated by Lineweaver-Burk plot and expressed relative to theV max for benzylpenicillin (taken as 100%). Abbreviations: PCN, benzylpenicillin; CER, cephaloridine; CTX, cefotaxime; CAZ, ceftazidime; AZT, aztreonam.